This undated graphic provided by Commonwealth of Australia (Geoscience Australia) Dr. Robin Beaman, James Cook University, shows the North-westerly view of the search area for the missing Malaysian Airlines Flight 370 at Broken Ridge, south-eastern Indian Ocean, which shows the Diamantina Escarpment dropping from about 800 meters to over 5000 meters in depth.

Seabed of Jet Hunt Zone Mostly Flat with One Trench

Two miles beneath the sea surface where satellites and planes are looking for debris from the missing Malaysian jet, the ocean floor is cold, dark, covered in a squishy muck of dead plankton and — in a potential break for the search — mostly flat.

The troubling exception is a steep, rocky drop ending in a deep trench.

Australian officials on Friday moved the search to an area 680 miles to the northeast of a previous zone as the mystery of Malaysia Airlines Flight 370 continued to confound.

The seafloor in this swath of the Indian Ocean is dominated by a substantial underwater plateau known as Broken Ridge.

The zone is huge: about 123,000 square miles, roughly the size of New Mexico. Still, while the previous search area housed a slew of underwater volcanoes whose magma constantly shifts the sea floor, the most recent suspected resting place of MH370 is more like a giant underwater plain.

The deepest part is believed to be 19,000 feet, within the range of American black box ping locators on an Australian ship leaving Monday for the area and expected to arrive in three or four days.

The black boxes were designed to emit locator pings for at least 30 days, and are projected to lose battery power — and thus their pings — by mid-April.

Searchers will be hoping that if the latest area turns out to be where the plane crashed, the fuselage did not go down on the southern edge of Broken Ridge.

That's where the ocean floor drops precipitously — more than 2 1/2 miles in places, according to Robin Beaman, a marine geologist at Australia's James Cook University.

"Let's hope the wreck debris has not landed over this escarpment — it's a long way to the bottom," Beaman said.

Precisely what the seafloor looks like in detail in the area of the new search is another in a long line of Flight 370 mysteries.